What’s A PHO? 9 Things You Probably Don’t Know About Trans Fats

Fats are a critical component of the diet, ranging from basic biological functions in metabolism maintenance as well as supporting glowing skin and shiny hair. Recently, partially hydrogenated oils (PHOs) have been the topic of much scientific and regulatory discussion, leading to a variety of news articles and media coverage. So why have PHOs garnered so much attention? Use this handy Q&A to help guide discussion on this “fat”tastic topic.

Let’s first start with the basics: what are dietary fats?

There are two types of dietary fats—saturated and unsaturated, which depend on the amount of hydrogen atoms that surround the fatty acid structure. This is called “saturation.”

Saturated fatty acids are "saturated" with hydrogens and are typically solid. Unsaturated fatty acids are not "saturated" with hydrogens and are typically liquid.

So, what exactly is a trans fat?

Trans fats are technically unsaturated, yet when formed, have characteristics more similar to saturated fats.

Trans fats are formed by adding hydrogen to unsaturated fats through a process called hydrogenation. The result is oils becoming more solid and stable at room temperature.

As an example, hydrogenating vegetable oil to make stick margarine is a process that increases the stability of fats. Therefore, the shelf life is increased.

What are some common sources of trans fats?

Trans fat found in our diet comes from two sources—foods from ruminant animals (such as sheep, goats, and cows) and some fats and oils used as ingredients in certain packaged foods.

Backup, I am confused…what is the difference between trans fats and partially hydrogenated oils (PHOs)?

While often used interchangeably, PHOs are a type of trans fat. PHOs are created by heating oil in the presence of hydrogen. PHOs are the largest source of trans fats in the diet.

I have heard a bunch about trans fats and PHOs in the news. What is this referencing?

In 2006, the FDA required labeling of trans fats on the Nutrition Facts panel.

In 2013, the FDA issued a Federal Register notice with a preliminary determination that PHOs would no longer be generally recognized as safe (GRAS).

Recently, in 2015, the FDA issued a final determination that trans fats are not GRAS and set a compliance date of three years to allow for reformulation or petitioning for specific use.

Can you walk me through the timeline of PHOs and trans fats?

PHOs were originally developed and patented in the 1900s as a more affordable replacement for animal fats due to shortage of butterfat at the time. Widespread use of PHOs began in the 1950s.

Increased use in the 1970s-1980s due to health consequences of saturated fats. Many were looking for alternative to saturated fat.